Project Summary/Abstract The Acute Respiratory Distress Syndrome (ARDS) is a major health concern that affects 200,000 patients a year and kills ~40% of the patients affected. Currently, there are no pharmacologic agents that improve outcome. Patients often present to the Emergency Room relatively early in the course of the illness, suggesting that lung injury might be prevented or even reversed, given timely administration of safe and effective therapeutics. As a practicing Emergency Physician, this clinical experience has motivated me to dedicate my career to the development and translation of biotechnology for the early diagnosis, prognostication, and treatment of ARDS. The current project involves a novel therapeutic approach, which provides protection in a mouse model of lung injury, and proposes three specific aims to further define its mechanism of action and advance its pre-clinical development. In ARDS, there is a reduction in the amount of Thrombomodulin (TM) expressed on the surface of pulmonary endothelial cells. This proteins normally partners with the Endothelial Protein Receptor (EPCR) to activate protein C, which in turn helps to mitigate inflammation, reduce plasma protein leak, and prevent microvessel thrombosis. The therapeutics described in the proposal augment this natural protective mechanism by binding to ICAM-1, an endothelial cell adhesion molecule upregulated in the setting of inflammation, and anchoring recombinant TM to the cell surface. Previous work demonstrates that this approach enables partnering of the targeted therapeutic with naturally expressed EPCR, boosting protein C activation and reducing the severity of lung injury when used prophylactically in a mouse model of ARDS. In the first specific aim, a series of in vitro microfluidic experiments are proposed to: 1. model the complex interactions which occur at the interface of flowing human blood and activated lung endothelium, and 2. clarify how ICAM-targeted TM works to reduce coagulation, immune cell adhesion, and vascular barrier dysfunction in these models. In the second aim, the synthesis and testing of a second generation of ICAM-targeted therapeutics is proposed, with the hypothesis that the new formulation will improve pharmacokinetics and prolong functional activity in the lung. In the third aim, extensive testing of ICAM- targeted TM is proposed in two distinct murine models of ARDS, to determine efficacy, dosing, therapeutic time window, safety, and mechanism of action.